Here is a neat little trick that I often find useful for renaming mp3 files with wrong names and correct tag titles. Just run this ruby script in the directory where you have stored your songs and it will read the tag title and rename the current file using it.

This script requires id3lib gem for ruby which can be installed simply by running the command:

gem install id3lib-ruby

One thing to notice in the script is that currently it works only on windows, but only with a little modification it can be made to work on other OSes as well (The only change I guess will be in the 5th line).